Friability testing of grinding wheels



1957 u. B. T ANGEMAN ETAL- 2,802,360

FRIABILITY TESTING OF GRINDING WHEELS Filed May 21, 1954 IN V EN TOR.

FRIABILITY TESTING on GRINDING WHEELS Urban B. Tangeman and NelsonEmmons III, Dayton, Ohio, assignors, by mesne assignments, to TheSheflield Corporation, a corporation of Delaware Application May 21,1954, Serial No. 431,326

2 Claims. (Cl. 73-38) This invention relates to a method for gauging theuniformity of the friable characteristic of different portions of agrinding wheel or the like.

One object of the invention is to provide a method for gauging therelative friability of different portions of a grinding wheel or thelike, in which a gauge head supplied with air from a regulated pressuresource is applied successively to different portions of a grinding wheelso that air is passed into exactly the same area at the differentportions tested. By comparing the rates of air flow at the differentportions tested the manner in which the grinding wheel will react whenformed by a crushing roll may be predetermined. It has been found thatgrinding wheels that give sufficiently large variations in air flow atdifferent portions are wheels that will not be uniformly crushed by acrushing roll.

Other objects and advantages of the invention will be apparent from thefollowing description, the appended claims, and the accompanyingdrawings.

In the drawings, in which the same reference characters have beenapplied to like parts in the several views;

Figure 1 illustrates the application of the particularly disclosedgauging head in carrying out the method of this invention to determinethe relative friability of different portions of a grinding wheel,

Figure 2 illustrates in longitudinal central section a particular gaugehead for use in carrying out the present method,

Figure 3 illustrates a fragment of the gauge head of Figure 2 shown inassociation with a portion of a grinding wheel in sealed interfittingrelationship therewith.

Figure 4 illustrates the lower end of the gauge head, and

Figure 5 shows a flow gauging instrument that may be used in conjunctionwith the illustrated gauge head for carrying out the present invention.

While the method may be practiced by a variety of apparatuses, there isherein shown and will now be described one such apparatus and infollowing the description of the apparatus the utility and applicationof the method will also be more clearly disclosed.

In the crush dressing of a grinding wheel for grinding workpieces of aparticular configuration a crushing roll is forced into the peripheralsurface of a grinding wheel while the roll and wheel rotate at the sameperipheral lpeed. It has been found that if the friability of thegrinding wheel is not uniform the crushing roll will meet with lessresistance at one portion of the wheel than another and the resultingwheel form will not be truly annular. The difiiculties involved ingrinding with such an irregularly formed wheel will be apparent. Therehas been no satisfactory previous method for predetermining theuniformity of the crushing reaction on the grinding wheel.

In accordance with the present method the relative friability ofdifferent portions of the grinding wheel before it is crushed isdetermined with precision and without affecting the grinding wheel. Incarrying out the present invention air from a controlled pressure sourceis passed atent 2,802,360 Patented Aug. 13, 1957 successively intodifferent portions of the wheel and the resulting air flows compared orgauged by means of a suitably calibrated instrument to give anindication of the friability characteristic. The gauge head is appliedin sealed relationship directly to the periphery or an active surface,or to the wheel sides near the periphery, and the resulting air flowsthat take place through the particular portions are compared. Byrepeating and comparing these measurements a study of the relativefriability characteristics of the grinding wheel and its adaptabilityfor crushing can be precisely determined.

Preferably the gauge head comprises a body 10 having a longitudinalcentral passage 11 therethrough. A tube 12 fitted about a reducedextension 14 of the body 10 leads through a gauging instrument 15 to asource of air under regulated pressure. Gauging instruments can beprovided which measure flow either by gauging the pressure drop across arestriction or by directly measuring the actual rate of flow, and assuch devices are well known it is unnecessary to explain here any of thedetails of the flow gauging device. The particular instrument 15 is onethat gives an indication of the air flow.

An annular resiliently yielding sealing member 16 is cemented to theother end of the body 10 within a recess 17. The member 16 is preferablya rubber ring of such. character that its surface when applied to thegrinding wheel will conform to all the surface irregularities of thegrinding wheel. The body 11 has an annular extension at 18 extendingalong the axis of the passage 11 and the annular sealing member 16 andterminating in a plane perpendicular to the axis of the passage 11 andthe passage through the sealing member 16. The outer surface of thesealing member 16 when free, as illustrated in Figure 2, extendsslightly beyond the annular extension 18. Grooves 19 pass radiallyacross the face of extension 18. An annular pocket 20 provided betweenthe sealing member 16 and the annular extension 18 communicates with thegrooves 19. The gauging head body 10 is flared at the end thereofadjacent the sealing member 16 for grasping by the operator and easyapplication in gauging.

Figure 3 illustrates the gauge head as applied to the side surface of agrinding wheel near the periphery or active surface, although it will beobvious that the peripheral surface itself may be tested by applying thegauge head directly to the periphery at different portions. It will beseen that the outward surface of the annular sealing member 16 has beenapplied under compression and conforms to the surface irregularities ofthe grinding wheel 25. The compressive application of this sealingmember 16 to the grinding wheel 25 is limited by the engagement of theannular extension 18 of the gauging head body 10 with the surface of thegrinding wheel. Because the compression is limited to the samepredetermined amount upon each application of the gauge head the sealingwill be the same and valid comparisons of the measurements are possible.When so applied under compression the sealing member 16 being resilientand yieldable will interfit in sealed relationship with the surfaceparticles of the grinding wheel and surface characteristics of the wheelwill not affect the gauging. Gauging air supplied through tube 12 willpass along the passage 11 of the gauging head, through the annularmember 16 and into and through the particular portion of the grindingwheel being gauged. At least a portion of the air will be collected inthe annular pocket 20 and pass radially out through the grooves 19. Ithas been found that a measurement of the fiow of air forced intodifferent wheel portions gives an accurate check of relative friabilityof the wheel portions and the adaptability of the wheel to crusheddressing. The porosity or permeability of the wheel portions willdetermine the flow and is directly related to the uniformity andrelative friable characteristic of checked portions of any particulargrinding wheel.

In Figure 1 the gauging head is illustrated as applied in carrying outthe method of this invention. In the position as shown in solid lines inFigure 1, the gauging head has been applied to a first portion of thegrinding wheel. The flow of air through the gauging head and through theparticular grinding wheel portion will be indicated on the instrument15. When the gauging head is moved to another portion of the grindingwheel as, for example, that shown in phantom lines, the instrument willagain indicate the resulting air flow as determined by thecharacteristics of that particular portion of the grinding wheel. Acomparison of the resultant flows will indicate the relative friabilitycharacteristics of the gauged portions of the grinding wheel. A completestudy of the characteristics of the grinding wheel 25 could be made byapplying the gauge head wherever a measurement is necessary. Theinstrument 15 can be calibrated as desired and, for

example, in a direct comparison measurement a calibration in terms ofcubic feet per minute of air flow through the grinding wheel portionscan be used.

' Through the application of the method taught by this invention thenondestructive testing of the relative characteristics of differentportions of a wheel can be made with precision. Because of thenon-destructive character of this method and its simple and economicalapplication, grinding wheels can be pretested for friability todetermine their adaptability to crush dressing and grinding, thusallowing their selection without expensive or wasteful procedures.Through its small size and configuration it can be readily applied byhand wherever a measurement is desired. The particular gauging headillustrated is extremely simple in construction and is adapted for along useful life in gauging both fiat and curved surfaces. The freeouter surface of the sealing member of the gauging head is provided toconform in yielding interfitting relationship with the surface of theparticular part portion being gauged and structure is provided to insurea uniform compressive engagement with the part surface, making possiblerepeated accurate gauging operations of this character which can bevalidly compared.

While the particular application of the method and the particular formof device herein described constitute a preferred application of themethod and a preferred device for carrying the method out, it is to beunderstood that this invention is not so limited and that changes may beapplying the conduit in sealed relationship with the same surface areaat another location on the same grinding wheel and passing air under thesame pressure from the conduit into and through such other grindingwheel portion, and gauging the resultant air flow through such othergrinding wheel portion, whereby the relative friability of the gaugedWheel portions is determined.

2. A method of non-destructive gauging of relative characteristics ofdifferent portions of the surface of a grinding wheel or the like formedgenerally of abrasive work forming particles, bond and voidstherebetween, to determine the uniformity of distribution of materialtherein and its characteristics during dressing, forming operations, orthe like, comprising the steps of first supplying air under pressurethrough a predetermined small area of the surface at a first locationtherealong, gauging the how of air into and through the surface betweenthe abrasive particles at said one location, supplying air underpressure through the surface at other locations therealong but throughthe same small area for precise comparison I of results, gauging theflow of air into and through the surface and between the abrasiveparticles at said other locations, and comparing the resultant air flowsat the

